1. Field of the Invention
The present invention relates to a filter for photoelectric touch panel adapted to form a matrix of infrared beams in front of its screen and, when a finger or a pen touches the screen, the infrared beams corresponding to the touched position are shielded and the coordinates are input to a computer.
2. Description of the Prior Art
As a filter for a photoelectric touch panel of the described type such as shown in FIG. 3 has in general been in use. Referring to FIG. 3, 1 denotes a filter. The filter 1 formed into a frame and having a smooth surface is disposed in front of arrays 2 and 2a of aligned LEDs 3, 3 as light emitting elements and aligned phototransistors 4, 4 as photosensitive elements. The arrays are arranged on a framework on the circumference of a screen.
Now, chiefly concerning the LEDs 3 and phototransistors 4 located at end portions of the arrays 2 and 2a, it is found out that, while some beams of light emitted from the LEDs 3 will straightly advance and be properly received by the phototransistors 4, some other beams emitted from the same will advance so as to be reflected at around the center of the filter portion 1b perpendicularly crossing the filter portion 1a disposed in front of the LED 3 and erroneously received by the phototransistors 4. In such a case, even if the beam advancing straight can be shielded, the shielding is not effected as an input to a computer and such was a cause of malfunction of the apparatus in the prior art.